package com.chen.bpsptsystem.utils;

/**
 * @CLASSNAME OrderUtil
 * @DESCRIPTION 描述
 * @AUTHOR chen
 * @DATE 2019-02-18 17:48
 **/
public class OrderUtil {
    private long workerId;
    private long datacenterId;
    private long sequence;

    public OrderUtil(long workerId, long datacenterId, long sequence) {
        // sanity check for workerId
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException( String.format( "worker Id can't be greater than %d or less than 0", maxWorkerId ) );
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException( String.format( "datacenter Id can't be greater than %d or less than 0", maxDatacenterId ) );
        }
        //System.out.printf( "worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d", timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId );
        this.workerId = workerId;
        this.datacenterId = datacenterId;
        this.sequence = sequence;
    }

    private long twepoch = 1288834974657L;

    private long workerIdBits = 5L;
    private long datacenterIdBits = 5L;
    private long maxWorkerId = -1L ^ (-1L << workerIdBits);
    private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    private long sequenceBits = 12L;

    private long workerIdShift = sequenceBits;
    private long datacenterIdShift = sequenceBits + workerIdBits;
    private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    private long sequenceMask = -1L ^ (-1L << sequenceBits);

    private long lastTimestamp = -1L;

    public long getWorkerId() {
        return workerId;
    }

    public long getDatacenterId() {
        return datacenterId;
    }

    public long getTimestamp() {
        return System.currentTimeMillis();
    }

    public synchronized long nextId() {
        long timestamp = timeGen();

        if (timestamp < lastTimestamp) {
            // System.err.printf( "clock is moving backwards.  Rejecting requests until %d.", lastTimestamp );
            throw new RuntimeException( String.format( "Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp ) );
        }

        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                timestamp = tilNextMillis( lastTimestamp );
            }
        } else {
            sequence = 0;
        }

        lastTimestamp = timestamp;
        return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
    }

    private long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    private long timeGen() {
        return System.currentTimeMillis();
    }

    //---------------测试---------------
    public static void main(String[] args) {
        OrderUtil worker = new OrderUtil( 1, 1, 1 );
        for (int i = 0; i < 100; i++) {
            System.out.println( worker.nextId() );
        }


    }
}
